Apparatus and method for pulling cable

ABSTRACT

A primary device placed at the upstream end of a duct and a relay device placed at an access point pull a cable through respective duct segments. The pulling speed of the primary device is controlled by an operator. The pulling speed of the relay device is variable in response to movement of the cable by the primary device to maintain equilibrium between the pulling speeds of the devices. The pulling tension exerted upon the cable by each device is monitored and discontinued upon reaching a predetermined maximum value. At the inlet to the second segment, lubricant is supplied to the cable at a quantitative rate which is proportional to the pulling speed.

CROSS REFERENCE TO RELATED APPLICATIONS

The instant application is a division of Ser. No. 08/238,327 filed 5 May1994 now U.S. Pat. No. 5,533,711 which is a Continuation-in-Part of thecommon inventor's co-pending application Ser. No. 07/853,514 filed 18Mar., 1992 and entitled APPARATUS AND METHOD FOR PULLING CABLE, now U.S.Pat. No. 5,324,006 which was a Divisional Application of the commoninventor's co-pending application Ser. No. 07/532,793 filed 4 Jun. 1990and U.S. Pat. No. 5,152,506.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to the installation of signal transmission cable.

More particularly, the present invention relates to method and apparatusof the type especially adapted for pulling an extended length of fiberoptic cable through a subterranean duct.

In a further and more specific aspect, the instant invention concernsimprovements in methods and apparatus according to the foregoing formonitoring and sensing selected characteristics of the cable duringpulling and modulating the pulling accordingly.

2. Prior Art

Various types of cable especially adapted for the transmission of audioand visual signals are well known. Conventional cable, for example,incorporates metallic wire as the medium for transmission of signals inthe form of electric current. More recently, the art has directedattention to fiber optic cable in which encoded light pulses aretransmitted through thin fibers of glass, plastic or other transparentmaterial.

Signal transmission cables are subject to varying installation schemes.Especially common are airborne installations and undergroundinstallations. In an airborne scheme, the cable is suspended betweensupporting members such as poles. In an underground system, the cable isburied. Certain types of cable are suitable for direct installation.Others require a protective encasement.

In an underground or subterranean system it is generally preferred thatthe cable resides within a conduit commonly termed a subduct. Thesubduct provides protection for the more fragile types of cable. Thesubduct also facilitates maintenance of the cable and may accommodatesubsequent installation of additional cable.

Typically, a subterranean system includes a subduct of extended length,frequently many miles, which has been buried by conventional practicesuch as plowing, trenching and filling. Accessibility is provided by aseries of manholes or vaults, each having an opening at ground level.Entrance and exit vaults reside at respective ends of the subduct.Access vaults are placed at spaced locations intermediate the entranceand exit vaults.

The several access vaults divide the subduct into plurality of segments.Each segment has an entrance or upstream end at one vault and an exit ordownstream end at the subsequent vault. A pull line extends through thesubduct. A slack length of the pull line, commonly incorporated into thesubduct prior to burial, is available within each vault.

The signal transmission cable is pulled through the subduct by the pullline. The cable is supplied by a spool thereof placed near the entrancevault. The upstream end of the pull line and the cable, in sequence, aredrawn through the subduct. The operation is completed when thedownstream end of the transmission cable is received within the exitvault and the pull line is stowed, usually upon a take-up spool.

It is desirable that cable be installed in continuous runs of maximallength. Splicing is a laborious, expensive and time consuming task.Additionally, each splice adversely effects transmission quality. Theforegoing is substantially more pronounced in fiber optic cable than inwire cable. Further limitations, restricting the length of a singlepull, are the result of the inherent tensile weakness of fiber opticcable. Accordingly, the prior art has devised various techniques forpulling extended lengths of transmission cable, especially fiber opticcable.

In accordance with one scheme, the installation is accomplished by asequence of pulls and stores. Initially, cable is pulled from a supplyspool through the first segment of the subduct and stored at the firstaccess vault. Subsequently, the cable is pulled through the secondsegment and stored at the second access vault. The process is repeatedin sequence temporarily storing cable at each access vault andsubsequently pulling the cable through the adjacent downstream segment.

More recently, the art has provided means and methods for simultaneouslypulling a cable through at least two adjacent segments of a subduct. Thepull line is wound about the capstan wheel of a winch placed in the exitvault and in each access vault. The several capstan wheels aresimultaneously driven by individual hydraulic motors, each powered byhydraulic fluid of pre-set maximum pressure. Tension exerted by adownstream winch pulls the cable into frictional driving engagement withthe rotating wheel of the adjacent upstream winch.

Although providing certain advantages over previous efforts, themultiple winch system described above is not considered to be a panacea.Initially it is noted that set-up is laborious and time consuming,requiring that each winch be lowered into a vault and frequentlyrequiring partial disassembly and reassembly. Further, since the capstanwheel is driven by a motor which responds to a predetermined fluidpressure system it is possible that excessive tension can be exertedupon the cable. Also the system requires the constant observation of aworkman for adjusting and controlling each winch. Other shortcomings arenoted.

In an airborne scheme, the cable is suspended between supporting memberssuch as poles. Typically, a support cable is already present, and themore delicate signal transmission cable is secured thereto. First,however, the transmission cable must be pulled along the support cable.Conventionally this has been accomplished by attaching one end of a pullline to an end of the transmission cable, and attaching the other end ofthe pull line to a pull vehicle such as a truck or the basket of a boomtruck. The pull cable is generally run through pulleys coupled to thesupport cable. Additional pulleys are added as the cable is pulled offits storage spool. This is a very simple and effective method ofstringing cable for short distances, but, as discussed above forsubterranean cable work, it is desirable that cable be installed incontinuous runs of maximal length. Splicing is a laborious, expensiveand time consuming task. Additionally, each splice adversely effectstransmission quality. The length of a single pull is limited by theinherent tensile weakness of transmission cable, and especially limitedby fiber optic cable. When that limit is reached, the cable must becollected such as on a take up spool, and a new run begun. This can be atedious, time consuming procedure, and very difficult to implement if apull truck is used.

Another problem which arises from using a vehicle to pull a cable, issubjecting the cable to a tension force in excess of a recommendedvalue. A large pull vehicle can greatly exceed the tensile strength of afiber optics cable, damaging the cable before the operator is even awarethere is a problem. This has been overcome to some extent by the use oftensometers coupled between the pull vehicle and a cable. Typically thetensometer is coupled to a display within the cab of the vehicle andshows the tension on the cable as it is pulled. When the tension reachesa predetermined level, the vehicle operator stops pulling. This workswell when the operator is paying close attention to the display as hedrives, and if he can stop the vehicle at any time along the route ofthe cable run. Generally, however, the operator cannot stop in certainspots, for example on railroad tracks, intersections or the like.Therefore, the operator must stop where he can, before he exceeds therecommended tension. Furthermore, if a snag develops while pulling thecable, the recommended tension can be greatly exceeded before theoperator can react to the warnings from the display, even if he ispaying close attention.

It would be highly advantageous, therefore, to remedy the foregoing andother deficiencies inherent in the prior art.

Accordingly, it is an object of the present invention to provideimprovements in the installation of signal transmission cable.

Another object of the invention is the provision of improvementsespecially adapted for the installation of fiber optic cable in asubduct.

And another object of the invention is to provide an improved cablepulling system which operates in response to actual cable tension.

Still another object of the instant invention is the provision ofimproved means whereby an upstream pulling means is actuated andregulated in response to a downstream pulling means.

Yet another object of the invention is to provide means for regulatingthe speed of operation of an upstream pulling means in response to thespeed at which a cable is pulled by a downstream pulling means.

Yet still another object of this invention is the provision of means formonitoring the upstream stress upon a cable and maintaining the stressbelow a predetermined value.

And a further object of the invention is to provide a system which isself-regulating and does not require constant observation and control bya workman.

Still another object of the immediate invention is the provision of anintegrated system including various ancillary functions such aslubricating the cable and taking-up the expended pull line whichfunction at a rate proportional to a rate at which the cable is pulled.

Yet a further object of the invention is to provide a cable pullingsystem that can be emplaced and made operational with comparativeconvenience and ease.

And yet another object of the invention is the provision of improvementsaccording to the above which are relatively unencumbered andinexpensively practiced.

And another object of the present invention is to provide an apparatusfor use on pull vehicles, to prevent exceeding a predetermined tensionplaced on a cable being pulled.

SUMMARY OF THE INVENTION

Briefly, to achieve the desired objects of the instant invention inaccordance with a preferred embodiment thereof, provided is a primarydevice and a relay device which cooperate as an apparatus for pulling acable through a duct having a downstream end, an upstream end, and anaccess point intermediate the ends dividing the duct into a firstsegment adjacent the upstream end and a second segment adjacent thedownstream end. The primary device exerts a first pulling tension uponthe cable to pull the cable at a pulling speed from the downstream endof the duct. The relay device is responsive to the pulling speed of theprimary device for exerting a second pulling tension upon the cable topull the cable at a relay speed from a downstream end of the firstsegment and for availing the cable to the upstream end of the secondsegment.

More specifically, the relay device includes first means for pulling thecable from the downstream end of the first segment and relaying thecable from to the upstream end of the second segment and second meansfor controllably varying the first means to move the cable at a relayspeed which is variable and proportionate to the pulling speed imposedby the primary device. The second means is responsive to a differentialbetween the pulling speed and the relay speed to control the first meansto pull the cable at a relay speed which is in equilibrium with thepulling speed. Equilibrium is achieved by causing the first means toaccelerate when the pulling speed exceeds the relay speed and todecelerate when the pulling speed is lesser than the relay speed.

In accordance with a preferred embodiment thereof, the relay deviceincludes cable handling means for exerting the second pulling tensionupon the cable and variable drive means for driving the cable handlingmeans to move the cable at the relay speed. Further included are cablesensing means responsive to a differential between the pulling speed andthe relay speed and control means responsive to the cable speed sensingmeans for varying the speed of said drive means to achieve equilibriumbetween the pulling speed and the relay speed. The cable sensing meansis moveable in a first direction in response to the pulling speed beinggreater than the relay speed and in a second direction in response tothe pulling speed being less than the relay speed. The control meansincreases the speed of the drive means in response to the sensing meansmoving in the first direction and decreases the speed of the drive meansin response to the sensing means moving in the second direction. Biasingmeans normally urge the sensing means in the second direction.

Further, in accordance with a preferred embodiment thereof, the primarydevice and the secondary device include means for limiting therespective pulling tensions to a predetermined value. Preferably, thereare provided first means for monitoring tension exerted upon the cableby the cable handling means and second means for controlling operativeresponse of the cable handling means to the drive means, the secondmeans being responsive to the first means whereby the tension exertedupon the cable is maintained below a predetermined value. A preferredfirst means includes a moveable member for receiving the cablethereagainst and biased against movement by a force of predeterminedvalue. The member is urged to move in response to the tension upon thecable exceeding the predetermined value. In response to movement of themoveable member, the second means moderates operative response of thecable handling means to the drive means. A preferred second meansincludes control means for controlling the motive energy supplied to amotor for driving the cable handling means. The force opposing movementof the moveable member may be variably adjustable to a selectedpredetermined value.

The apparatus of the instant invention may also include a pusher devicefor pulling the cable from a supply reel thereof and feeding the cableto the upstream end of the duct. Tension exerted upon the cable by thepusher device is substantially less than the pulling tension of eitherthe primary device or the relay device. Also provided are means fordriving a take up reel to receive excess cable from the primary deviceat a tension which is less than the pulling tension exerted by theprimary device. Further provided are means for lubricating the cable ata quantitative rate which is proportional to the speed of movement ofthe cable through the duct. A preferred lubricating means includes afitting for receiving the cable therethrough prior to entry into theduct and a pump for supplying lubricant to the fitting from a reservoirthereof. The pump is driven by a motor which resides in series with thecable handling means and the drive means to operate at a proportionalspeed.

In accordance with a more specific embodiment of the invention,especially adapted for use in connection with an undergroundinstallation, the primary device is positioned adjacent an access vaultand the relay device is positioned adjacent an access vault. Preferably,each device includes a frame for supporting the cable handling meansupon the respective vault. First guide means are provided for receivingthe cable from the respective duct segment and guiding the cable to therespective cable handling means. The relay device further includessecond guide means for receiving the cable from the cable handling meansand guiding the cable to the adjacent downstream duct segment.

In accordance with yet another feature of a cable pulling system of thepresent invention, provided is a drive out controller apparatus for usewith a pulling vehicle to prevent subjecting a cable to a tension forcegreater than a predetermined value. The apparatus includes a tensionrelief mechanism mountable on the vehicle, and having a locked state andan unlocked state, a tensometer engaging said pull line for gauging thetension placed thereon, and generating a signal indicating a tensionforce value and a control system for switching said tension reliefmechanism to said unlocked state upon receiving a signal from saidtensometer indicating a predetermined tension value has been reached.

More specifically, the tension relief mechanism includes a spoolrotatably mountable on said pulling vehicle, said spool rotatable by apulling force generated by pulling said cable, a stop mechanism coupledto said spool for preventing rotation of said spool with said tensionrelief mechanism in said locked state and permitting rotation of saidspool with said spool in said unlocked state and a brake coupled to saidspool for subjecting said spool to a drag in the unlocked state.

Stop mechanism includes a pin movable between an extended position inwhich said pin engages said spool, preventing rotation thereof, and aretracted position in which said pin disengages said spool, allowingrotation thereof, and a motor for moving said pin between said extendedposition and said retracted position, said motor actuated by saidcontrol system. The brake adjustably engages said spool for increasingand decreasing the amount of said pulling force required to rotate saidspool.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further and more specific objects and the advantagesof the instant invention will become readily apparent to those skilledin the art from the following detailed description of preferredembodiments thereof taken in conjunction with the drawings, in which:

FIG. 1 is a semi-schematic elevational view of a cable pulling apparatusconstructed in accordance with the teachings of the instant invention asit would appear during use for installing a cable in a subduct system,portions of the illustration being broken away and in section;

FIG. 2 is an enlarged fragmentary frontal perspective view of theintermediate device seen in connection with the apparatus of FIG. 1;

FIG. 3 is an enlarged side elevational view of the upper portion of thedevice seen in FIG. 2;

FIG. 4 is an enlarged fragmentary rear perspective view of the deviceseen in FIG. 2;

FIG. 5 is an enlarged front elevational view of the device of FIG. 2,portions thereof being broken away for purposes of illustration;

FIG. 6 is a fragmentary elevational view generally corresponding to thelower portion of the view of FIG. 5 and showing an alternate embodimentthereof;

FIG. 7 is a partial perspective view of a winding and storage apparatususeful in connection with the invention seen in FIG. 1;

FIG. 8 is a partial perspective view of an alternate winding and storageapparatus;

FIG. 9 is a schematic illustration of a control system used in theoperation of the apparatus of FIG. 1;

FIG. 10 is a view generally corresponding to the view of FIG. 3 andillustrating an alternate embodiment thereof;

FIG. 11 is a view generally corresponding to the illustration of FIG. 5and showing an alternate embodiment thereof;

FIG. 12 is a diagrammatic illustration useful in explaining theoperation of the cable pulling apparatus seen in FIG. 1;

FIG. 13 is a diagrammatic view useful in explaining the self regulatingspeed operation of one of the units seen in FIG. 1;

FIG. 14 is a perspective view of a drive out controller being used on apull vehicle stringing cable in an airborne situation;

FIG. 15 is an enlarged perspective view of a tension relief mechanismand tension sensing means in broken away relation;

FIG. 16 is a perspective view illustrating an alternate embodiment oftension sensing means in broken away relationship with control means;

FIG. 17 is a perspective view of another embodiment of a portion of adrive out controller, illustrating a tension relief mechanism andtension sensing means;

FIG. 18 is a perspective view illustrating a relay unit employed toassist in stringing an airborne cable;

FIG. 19 is a perspective view of a friction drive accessory for use incombination with a relay unit for taking up the expended pull line; and

FIG. 20 is a perspective view of a friction drive accessory for use incombination with a relay unit for driving a pump to supply lubricant tosaid cable being pulled in a subterranean scheme.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Turning now to the drawings in which like reference characters indicatecorresponding elements throughout the several views, attention is firstdirected to FIG. 1 which illustrates facilities of the type commonlyprepared for installation of a signal transmission cable in connectionwith an underground or subterranean system. Seen is an entrance vault20, an exit vault 22 and an intermediate access vault 23. Residingwithin an excavation, entrance vault 20 is defined by continuous uprightside wall 24 terminating with an upper open end 25 residing atapproximately ground level as designated by the reference character 27.Similarly constructed and placed, exit vault 23 includes sidewall 28with open top 29 and access vault 23 includes sidewall 30 with openupper end 32.

Subduct 33, a conduit generally fabricated of a plastic material such aspolyethylene, communicates between entrance vault 20 and exit vault 22,having inlet end 34 projecting through sidewall 24 and outlet end 35projecting through sidewall 28. Not extending continuously throughaccess vault 23, subduct 33 is divided into a first segment 37 extendingbetween entrance vault 20 and access vault 23, and a second segment 38extending between access vault 23 and exit vault 22. Outlet end 39 offirst segment 37 and inlet end 40 of second segment 38 penetratesidewall 30.

For purposes of illustration, a single representative access vault isshown intermediate the entrance vault and the exit vault. In actualpractice, the installation may include several access vaults. Thespacing and number of access vaults are dependent upon numerous factorsincluding the total length of the installation, the type of cable beinginstalled, the type of subduct and contour of the terrain. Ideally, theoverall length of the installation coincides with the length of cablecarried upon a supply spool. It is also noted that the illustratedinstallation may comprise a single section of a substantially longerinstallation in which the exit vault subsequently becomes the entrancevault as seen with reference to the continuation of the subduct 33aprojecting through the sidewall 28 of exit vault 22.

The foregoing is set forth for purposes of orientation and reference inconnection with the ensuing detailed description of preferredembodiments of the instant invention. The structure described isintended to be typically representative of subterranean signaltransmission cable systems in general. Further and more specificdetails, as well as analogous structures, will be readily apparent tothose skilled in the art.

With continued reference to FIG. 1 there is seen, in semi-schematicrepresentation, apparatus constructed in accordance with the teachingsof the instant invention for installing signal transmission cable in theabove described subterranean installation. Provided by the instantinvention is a primary unit, a relay unit and a pusher unit generallydesignated by the reference characters 50, 52 and 53, respectively.Primary unit 50 functions in cooperation with exit vault 22 while pusherunit 53 is positioned adjacent entrance vault 20. A relay unit 52 isassociated with each access vault 23. The units cooperate to pull signaltransmission cable through subduct 33.

Conventionally, the signal transmission cable 54 is provided by a supplyreel 55. A pull line 57, also referred to as a pulling tape, extendsthrough subduct 33, having been previously placed in accordance withvarious procedures as will be readily apparent to those skilled in theart. Further, in accordance with prior art practice, the end of pullline 57 projecting from inlet end 34 of subduct 33 is secured to the endof cable 54 extending from reel 55 to form a continuous elongate member.The units of the instant invention cooperate to pull the elongatemember, pull line 57 and subsequently signal transmission cable 54,through subduct 33. As the operation proceeds, excess or used pull line57 is wound and stored upon take-up reel 58. The instant apparatus isespecially sensitive to the more fragile types of signal transmissioncable such as fiber optic cable.

The several units of the instant invention cooperate to pull theelongate member through subduct 33 in a direction indicated by thearrowed line A. For purposes of orientation and reference, arrowed lineA is assumed to be pointing in a downstream direction. Accordingly, theinlet end of the subduct and of each segment thereof is considered to bethe upstream end. Similarly, the outlet end of the subduct end of eachsegment thereof is considered to be the downstream end.

Briefly, pusher unit 53 pulls cable 54 from supply reel 55 and feeds thecable to the first segment 37 of subduct 33. Primary unit 50 initiallydraws or pulls pull line 57 from the second segment 38 of subduct 33 tobe received by the take-up reel 58. Relay unit 52 draws the elongatemember, initially pull line 57 and subsequently cable 54, from segment37 and feeds the member thus pulled to second segment 38. A completeunderstanding of each unit and the interaction therebetween as anintegrated cable pulling apparatus will be had with regard to thedescription which follows.

For reasons of simplicity and economy relating to manufacture and tooperation, primary unit 50 and relay unit 52 share numerous commonelements. An understanding of both units can be had with reference to adescription of relay unit 52, which will now be made in detail.

Referring to FIG. 2, it is seen that relay unit 52 is a duplex structurehaving a cable handling unit generally designated by the referencecharacter 60 and a power unit generally designated by the referencecharacter 62. Cable handling unit 60, as further seen in FIGS. 3 and 4,includes a frame 63 having a pair of spaced apart, preferably parallelground support members which are of sufficient length to span and bearupon the upper end 32 of access vault 23. A lifting bracket 67,preferably an inverted U-shaped member which alternately functions as ahand grip or attachment means for mechanized lifting equipment, issecured approximate each end of the support members 64 and 65. atransverse member 68 extends between support members 64 and 65, havingrespective ends thereof affixed to an intermediate point of the member64 and 65. An upright support member 69 extends upwardly inward fromground support member 64. A mirror image upright support member 70extends upwardly inward from ground support member 65. Cylindricalmember 72 is affixed to the upper ends of upright support members 69 and70. Preferably, frame 63 is fabricated as a weldment of metallicelements especially incorporating tubular members.

Cylindrical member 72 functions as a housing or support bracket forrotary motor 73 having forwardly extending drive shaft 74. In accordancewith the immediately preferred embodiment of the invention, motor 73 isof the conventional hydraulic type which includes inlet port 75 andoutlet port 77 adapted for the attachment of the customary hydraulicfluid lines. Capstan wheel 80, having rim 82 carried by hub 83, isaffixed in driving engagement to drive shaft 74 of motor 73. Inaccordance with conventional practice, concave circumferential surface84 extends about rim 82. Preferably, the axis of motor 73 andconsequently the axis of rotation of capstan wheel 80, as represented bythe broken line B, is angularly disposed to the horizontal, as definedby support member 64 and 56, to extend upwardly forward. Furtherdescription of the port 75 and 77 associated with motor 73 and of theangular disposition of axis B will be made presently.

Additional attention is now directed to FIG. 5 which shows an infeedcable guide and an outfeed cable guide designated by the referencecharacters 85 and 87, respectively, depending from frame 63 to residewithin vault 23. Being analogously constructed and placed in mirrorimage arrangement, each guide includes a pair of spaced apart sideplates 88 and 89 having a plurality of concave rollers rotatablysupported therebetween. Preferably each cable guide 85 and 87 isquadrantal for guiding the cable through a turn of 90.

Bracket 92 residing at an intermediate location along transverse member68, supports depending support member 93 the lower end of which ispivotally affixed to the lower ends of cable guides 85 and 87 by pin 94.It is preferred that depending support member 93 extends along anupright axis represented by the broken line C which intercepts the axisof rotation B of capstan wheel 80. It is also preferred that dependingsupport member 93 is selectively adjustable at elevated and lowerpositions as represented by the double arrowed line D. Similarly, asecond depending support member 95 having a lower end thereof pivotallysecured to the upper end of outfeed cable guide 87 by pin 97 isadjustably carried by a second bracket 98 which is also affixed totransverse member 68.

In accordance with the immediately preferred embodiment of theinvention, the upper end of infeed cable guide 85 is secured totransverse member 68 by means of a hydraulic piston and cylinderassembly 99. Preferably, cylinder 99 is securable to transverse member68 at selectively adjustable vertical positions as also represented bythe double arrowed line D. The free end of operating rod 100, dependingfrom the piston within the cylinder 99 is secured to the upper end ofcable guide 85 by pin 102. Accordingly, with base 63 resting upon end 32of sidewall 30, cable guides 85 and 87 are adjustably positionablewhereby the lower ends are in substantial tangential alignment withsubduct 33. It is noted that the upper end of each cable guide is insubstantial tangential alignment with the circumferential surface 84 ofcapstan wheel 80.

Upper support member 105 includes upright portion 107 extending upwardlyfrom cylindrical member 72 and bifurcated terminal portion 108. Terminalportion 108 is angularly disposed to portion 107 to extend upwardlyrearward therefrom. Arm 109 extends forwardly from upper support member105 at a location spaced above capstan wheel 80. At the rearward end,arm 109 is received within bifurcated portion 108 and pivotally securedthereto by pin 110. Intermediate cable guide 112 is carried at theforward end of arm 109. Being generally analogous to the previouslydescribed cable guides, intermediate cable guide 112 includes a pair ofarcuate side plates 113 and 114 having a plurality of concave rollers115 rotatably supported therebetween. Preferably, intermediate cableguide 112 extends through an arc of approximately 180 whereby the endsare in substantial tangential alignment with the surface 84 of capstanswheel 80. It is also preferred that intermediate cable guide 112 issubstantially aligned with the forward portion of surface 84. Spring117, in compression between arm 109 and flange 118 projecting fromsupport member 105, biases arm 109 and intermediate cable guide 112 inan upward direction as indicated by the arrowed line E. Adjusting screw119 changes the effective length of spring 117 in accordance withconventional practice as will be readily appreciated by those skilled inthe art.

Power unit 62 is best described with reference to FIG. 2 which showsbase 120 upon which is supported drive unit 122 and lubrication unit123. Drive unit 122, as further illustrated in FIG. 4, includes internalcombustion engine 124 having fluid pump 125 secured thereto in drivingengagement. Fuel for internal combustion engine 124 is contained withintank 127 while reserve hydraulic fluid is contained within reservoir128, both of which are supported upon base 120. Although other forms ofpower producing units are perceived by the instant invention, aninternal combustion engine is preferred for reasons of versatility andself-containment as best adapted for use in remote areas.

Fluid pump 125 is of the conventional commercially available type havingselectively variable pressure and volume output. Exemplary is the unitdistributed by Oil Gear Company and designated Hydura Pump, Model No.PVW-06. Output of pump 125 is controlled by control lever 129 which ismovable in directions indicated by the double arrowed arcuate line F.For purposes of illustration, control lever 129 is shown at anintermediate position. In response to movement in a direction towardengine 122, output of pump 125 is increased while, conversely, output isdecreased in response to movement of lever 129 in direction away fromengine 122. At the extreme of movement in the decreasing direction,output from unit 125 is ceased. At the extreme of movement in theincreasing direction maximum output is achieved. A preferred exemplarymaximum output is a pressure of approximately 2,000 pounds per squareinch with a flow rate of approximately 11 gallons per minute. Forpurposes of reference, it is seen that pump 125 includes outlet port 130and inlet port 132.

Hydraulic motor 73 is of the conventional commercially available type. Arecommended exemplary motor is the one designated as WSI Model 360 Gearreducer distributed by Von Ruden Manufacturing Company. Supply or highpressure line 133 communicates between outlet port 130 of pump 125 andinlet port 75 of motor 73. Return or low pressure line 134 communicatesbetween outlet port 77 of motor 73 and inlet port 132 of pump 125.Accordingly, capstan wheel 80 is driven at a rotational speed and torqueresponsive to pump 125.

Control cable 135, a conventional commercially available product, hasrespective ends thereof secured to arm 109 and control lever 129 inaccordance with conventional procedures known to those skilled in theart. Accordingly, control lever 129 is movable in response to movementof intermediate cable guide 112. Intermediate cable guide 112 isreciprocally moveable in directions indicated by the double arrowed lineG. In response to the biasing of spring 117, intermediate cable guide112 is normally held in the full up direction, as previously indicatedby the arrowed line E. In response thereto control lever 129 is moved tothe extreme of the decreasing direction in which the output of pump 125is curtailed. As intermediate cable guide 112 moves downwardly, in thedirection indicated by the arrowed line H, the output of pump 125 iscontinuously increased. From the foregoing detailed description, it isapparent that movement of capstan wheel 80 is variable between idle anda rotation of predetermined maximum speed and torque.

It is preferred, as seen with particular reference to FIG. 5, that apilot operated shuttle valve 137 be placed in parallel with supply line133 and return line 134. The pressure at which valve 137 opens isselectively variable by adjustment screw 138. An exemplary valvecartridge for the immediate purpose is the device distributed by OilGear Company under the designation HSU 1200. For this purpose, teefitting 139 is placed in series with supply line 133 and tee fitting 140is placed in series with return line 134. Lines 142 and 143 communicatebetween the tee fittings 139 and 140, respectively, and throughoutshuttle valve 137.

Pressure line 144 communicates between hydraulic cylinder assembly 99and shuttle valve 137. Accordingly, valve 137 is responsive to pressurewithin cylinder assembly 99. To ensure that line 144 is filled withhydraulic fluid and that the piston is extended within the cylinderassembly 99, hydraulic fluid is fed into line 144 from any readilyavailable source, such as a charge pump associated with pump 125,through feed line 145. One-way check valve 147, in series with line 145,ensures that pressure in line 144 as a result of pressure exerted uponhydraulic cylinder assembly 99 is relayed to valve 137 and is notreturned to feed line 145. Pressure gauge 148 provides a visualindication of pressure within line 144. Cross or four-way fitting 149provides common attachment for valve 137, pressure line 144, feed line145 and pressure gauge 148.

Referring again to FIG. 2, it is observed that lubrication unit 123includes rotary hydraulic motor 150 placed in series with return line134 and drivingly engaged with fluid pump 152 for drawing lubricatingfluid from reservoir 153 and discharging the fluid through lubricationline 154. Lubricating fluid passing through lubrication line 154 isdischarged into fitting 155 through which pull line 57 and cable 54 passprior to entry into subduct segment 38. Preferably, one end of fitting155 is provided with a socket in the form of a counterbore for receivingthe inlet end of subduct segment 38. Being placed in series with supplyline 133, pump 150 is caused to run at a speed proportionate to therotation of capstan wheel 80. Accordingly, lubrication is supplied tofitting 155 at a proportionate flow rate. Further control over the speedof pump 150, and the rate of flow of the lubricating fluid, is exercisedby altering the ratio of the pulley and belt drive between pump motor150 and pump 152.

The foregoing detailed description of relay unit 52 includes variouselements which are common to primary unit 50. Especially noted are frame63, capstan wheel 80, motor 73, drive unit 122, infeed cable guide 85and the pressure responsive elements including hydraulic cylinderassembly 99 and relief valve 137 communicating between infeed cableguide 85 and drive unit 122. Peculiar to relay unit 52 are outfeed cableguide 87, intermediate cable guide 112 and lubrication unit 123. Anappreciation of the differences between primary unit 50 and relay unit52 is readily had with the understanding that primary unit 50 functionsonly to pull the cable while relay unit 52 additionally relays cable toa downstream unit.

An alternate arrangement for suspending infeed cable guide 85 belowframe 63 is illustrated in FIG. 6. The immediate embodiment of theinvention includes bracket 160 affixed to transverse member 68 for thepurpose of attachment of depending support member 162. Analogous to thearrangement between depending support member 93 and bracket 92,depending support member 162 is adjustable to selectively positionbracket 160 in directions indicated by the double arrowed line I. Pin163 pivotally connects the upper end of infeed cable guide 85 to thelower end of support member 162. Previously described hydraulic cylinderassembly 99 is pivotally affixed to the lower end of infeed cable guide85 by pin 164. Rod 100a, an elongated rod 100, extending from assembly99, terminates with foot 165 bearing against sidewall 30 of access vault23. Support cable 167, extending between transverse member 68 and thelower end of infeed cable 85, prevents sag and holds the lower end ofinfeed cable guide in position during set up.

Cylinder assembly 99 placed as seen in FIG. 6 or placed as seen in FIG.5 serves the same function. In the embodiment of FIG. 5, cylinder 99 isresponsive to force in the direction of arrowed line J. While placed inthe arrangement seen in FIG. 6, hydraulic cylinder 99 is responsive toforce in a direction indicated by the arrowed line K. As will beappreciated by those skilled in the art, both are the same forcemeasured at a different location.

various means, including prior art apparatus, are known for operatingtake-up reel 58 for winding and storing pull line 57. Provided by theinstant invention is an improved winding and storage apparatus as seenin FIG. 7 and generally designated by the reference character 170.Adapted to be mounted upon and transported by a motor vehicle, such as atruck, utility unit 170 includes base 172 supporting upright frame 173.Carried upon base 172, in common with previously described power unit62, is a drive unit 122 including internal combustion engine 124 andhydraulic pump 125 having volume control 129. As seen in greater detailin FIG. 9, pump 125 is a duplex device including system pump 174 andcharge pump 175. As previously described, system pump 174 suppliespressurized hydraulic fluid through supply line 133 for rotation ofmotor 73 and receives expended fluid through return line 134. As will beappreciated by those skilled in the art, charge pump 175 draws hydraulicfluid from reservoir 128 through make-up line 129 to supply system pump174 with hydraulic fluid to compensate for any losses thereof within thesystem. It will also be appreciated that charge pump 175 may be used tosupply hydraulic fluid to feed line 145 for supplying hydraulic pistonand cylinder assembly 99 as previously described.

In accordance with the immediately preferred embodiment of theinvention, pump 125 is under the immediate control of an operator. Forthis purpose there is provided operating rod 177 having an end engagedwith control lever 129 and terminating at the other end with hand knob178. At an intermediate location, operating rod 177 is slidablysupported by guide 179 for movement in directions indicated by thedouble arrowed line L. In response to movement of operating rod 177 asindicated by the double arrowed line L, operating lever 129 is caused tomove in corresponding directions previously indicated by the arcuatedouble arrowed line F. The immediate hand controlled drive unit isespecially devised for use in combination with primary unit 50 wherebythe primary unit 50 and each relay unit 52 is under control of a singleoperator as will be described in further detail presently.

Take-up reel 58 is drivingly engaged with axially extending axle shaft180. A terminal portion of axle shaft 180 extends outboard of eitherside of reel 58. Two pairs of rollers 182 and 183, supported by frame173 on respective sides of reel 58 removably receive and rotatablysupport respective terminal portions of shaft 180. Motor 184 rotatesshaft 180 and hence take-up reel 58 through a conventional belt andpulley arrangement 185. The normal direction of rotation of reel 58during take-up is indicated by the arcuate arrowed line designated bythe reference character M. Being driven by the low pressure or returnline 134, motor 184 rotates reel 58 at a speed which is proportionate tothe rotation of motor 73 but with substantially less torque.Accordingly, the stress or tension exerted on pull line 57 intermediateprimary unit 50 and take-up reel 58 is substantially less than thestress exerted upon either pull line 57 or cable 54 intermediate primaryunit 50 and the adjacent relay unit 52.

Further included in utility unit 170 is a hoist unit, generallydesignated by the reference character 190, supported by pedestal 192upstanding from base 172. Column 193 supported by pedestal 192 extendsupwardly therefrom and is journaled for rotation about the longitudinalaxis represented by the broken line N. Collar 194 having lug 210extending therefrom is drivingly engaged with column 193. Double actinglinear hydraulic motor 197, a conventional commercially availabledevice,.includes cylinder 198 having free end 207 pivotally secured toframe 173. Operating rod 200 extending from cylinder 198 terminates withclevis 202 pivotally affixed to lug 210. Operating rod 200 is caused tomove in reciprocal directions, extendable and retractable relativecylinder 198, in response to pressurized hydraulic fluid from line 145.The direction of flow of the hydraulic fluid and hence the direction ofmovement of rod 200 is determined by manually operable control valve203. Accordingly, column 193 is reciprocally rotatable about axis N indirections indicated by the double arrowed arcuate line 0.

A pair of spaced apart ears 204 project from column 193. Although onlyone ear 204 is illustrated it is to be understood that a second ear 204extends from column 193 in spaced parallel relationship. Boom 205includes a free end 207 and a fixed end 208 received between ears 204and pivotally secured thereto by pin 209. Lug 210 projects from boom 205at a location intermediate the ends thereof. Arm 212 terminates withupwardly projected bifurcated portion 213. A second double acting linearhydraulic motor 197a extends between column 193 and boom 205. The freeend 207 of cylinder 198 is received within and pivotally affixed tobifurcated terminal portion 213 of arm 212. Clevis 202 carried at thefree end of operating rod 200 receives and is pivotally connected to lug210. Supplied with pressurized hydraulic fluid from line 145 through asecond manually operable control valve 203a, hydraulic motor 197afunctions to pivotally raise and lower boom 204 in directions indicatedby the double arrowed arcuate line designated P.

A third double acting linear hydraulic motor 197b includes cylinder 198having end 199 pivotally secured to boom 205. Double grooved sheave 214is rotatably affixed to the free end of operating rod 200. A seconddouble grooved sheave 215 is rotatably secured proximate the free end207 of boom 205. A cable 217 terminating at the free end with hook 218is secured about the sheaves 214 and 215 in accordance with conventionalblock and tackle practice. Hydraulic motor 197b is manually operated bycontrol valve 203b. In response thereto, hook 218 is raised and loweredas indicated by the double arrowed line designated Q. Hoist unit 190, ofwhich further description will be made presently, is of sufficientstrength to lift the previously noted units designated by the referencecharacters 50, 52 and 53.

Referring more specifically to FIG. 9. it is noted that pump 125 and theseveral elements associated along the circuit defined by supply line 133and return line 134 are considered to comprise the main drive system.Pump 175, line 145 and the elements serviced thereby are designated asthe auxiliary system. The pressure of the hydraulic fluid supplied tothe valves 203 is monitored and regulated by pressure relief valve 220.Fluid circulating through the auxiliary system passes through filter 223and is returned to the main system, i.e. lines 133 and 134, throughcheck valves 224 and 225. Pressure within the auxiliary system ismonitored by a second pressure relief valve 22a which returns fluid tothe main system, i.e. line 133, through line 222. Also noted is checkvalve 225 installed in line 134 in parallel with motor 184.

FIG. 8 illustrates alternate means for rotating reel 58. Seen is arm 230pivotally connected at the fixed end 232 to bifurcated bracket 233 bypin 234. Although not specifically illustrated but as will be readilyappreciated, bracket 233 is secured to base 172 of utility unit 170.Rotary hydraulic motor 184a is supported at the free end 235 of arm 230.Wheel 237 covered with friction enhancing material 238 is drivinglycarried by shaft 239 of motor 184a. Tension spring 240, having one endengaged with arm 230 and another end appropriately secured to base 172,biases arm 123 downwardly in the direction indicated by the arrowed lineR.

In accordance with the immediately preferred embodiment of theinvention, motor 184a replaces motor 184 and may be substitutedtherefore in the schematic diagram of FIG. 9. Motor 184a drives wheel237 to rotate in the direction indicated by the arcuate arrowed line S.Accordingly, take-up reel 58 is rotated in a direction indicated by thearrowed line M. In response to the rotation of take-up reel 58, cable 57is drawn in the direction indicated by the arrowed line T and woundabout take-up reel 58. Wheel 237 is in frictional driving engagementwith cable 57 with a force predetermined by tension spring 240.Accordingly wheel 237 will slip should the speed of the incoming cabledecrease or stop. It is also noted that the speed at which line 57 istaken up remains constant regardless of the constantly increasingdiameter of the reel as a result of the cable wound upon reel 58.

The immediate embodiment of the instant invention also contemplatesmeans for evenly winding cable 57 upon take-up reel 58. With furtherreference to FIG. 8 there is seen a double lead screw 242 rotatablyjournaled in pillow blocks 243 which are in turn supported by frame 172.Follower 244 having guide pins 245 extending upwardly therefrom forreceiving cable 57 therebetween, is drivingly engaged with lead screw242. Conventional belt and pulley arrangement 247 drivingly couples leadscrew 242 with take-up reel 58.

Lead screw 242 and follower 244 cooperate in a manner analogous to theconventional familiar device commonly referred to as a level windmechanism. In response to rotation of screw 242, follower 244 movesreciprocally between the ends of screw 242 as represented by the doublearrowed line U. Cable 57 being guided by pins 245 passes back and forthacross take-up reel 58 concurrently with being wound. Accordingly, cable57 is placed in even coiled layers about take-up reel 58.

FIG. 10 illustrates alternate means for utilizing intermediate cableguide 112 to control capstan wheel 80. In general similarity to thepreviously described embodiment, the instant embodiment includes anupper support member 250 extending upwardly from cylindrical member 72and including upright portion 252 and rearwardly extending portion 253.Bifurcated portion 254 upstanding from rearwardly extending portion 253receives the rearward end of arm 255 and is pivotally secured thereto bypin 257. Intermediate cable guide 112 is carried at the forward end ofarm 255. Compression spring 258, having respective ends bearing againstrearwardly extending portion 253 and arm 255, biases arm 255 andintermediate cable guide 112 upwardly in the direction of arrowed line Eas represented by the broken partial outline designated 255a.

In accordance with the immediately preferred embodiment of theinvention, there is provided a variable pressure relief valve 260 havingbody 262 carried by rearwardly extending portion 253 of upper supportmember 250 and plunger 263 bearing against arm 255. Valve 260 isselectively variable by means of adjustment screw 264. Valve 260 isplaced in parallel with the hydraulic fluid supply to motor 73 by virtueof auxiliary lines 265 and 267. Line 265 communicates between valve 260and tee fitting 269 installed in supply line 133. Auxiliary line 267communicates between valve 260 and tee fitting 268 installed in returnline 134.

When intermediate cable guide 112 is in the fully elevated position, inthe direction of arrowed line E, arm 255 is spaced from plunger 263.Allowing valve 260 to function as a normal relief valve. At contactbetween arm 255 and plunger 263, control lever 129 is in the maximumincreasing direction. In response to further movement of arm 255,plunger 263 is depressed opening valve 260, thereby reducing the drivingforce to capstan wheel 80.

The typical subterranean signal transmission cable system illustrated inFIG. 1 includes vaults normally of a size for receiving that portion ofthe units of the instant invention depending below the frame. Facilitiesincluding vaults having a substantially smaller opening are also known.FIG. 11 illustrates a portion of such a system including vault 270defined by sidewall 272 having relatively small open top 273. In allother respects, the system is analogous to the previously describedsystem.

For use with vaults of the type illustrated, there is provided asub-frame 274 having ground support members 275 and 277 from whichextend upright support members 278 and 279, respectively. The normalground support members 64 and 65 of frame 63 are supported by sub-frame274 at an elevation whereby infeed cable guide 85 resides above groundlevel 27. It is noted that in the immediate embodiment outfeed cableguide 87 has been removed. It is also noted that, for purposes ofillustration, the cable is being pulled in a direction counter to thedirection in FIG. 1 as indicated by the arrowed line A.

Further provided by the instant embodiment are infeed guide tube 280 andoutfeed guide tube 282 which communicate between subduct 33 and relayunit 52. Infeed guide tube 280 is also used in connection with primaryunit 50. Infeed guide tube 280 includes an enlarged inlet end 283 whichis received over the end 40 of subduct segment 38. Outlet end 284 ofinfeed guide tube 280 receives the lower end of infeed cable guide. Alow friction and abrasion resistant material, infeed cable tube 280guides the cable from segment 38 to infeed cable guide 85. Similarly,outfeed cable guide tube 282 includes an enlarged end 285 for receivingend 39 of subduct segment 37 and bell mouthed inlet end 287 forreceiving cable 57 from capstan wheel 80. The functioning of unit 52, aspreviously described, remains unchanged.

Referring again to FIG. 1, it is seen that pusher unit 53 includes frame292 supporting internal combustion engine 122 drivingly engaged withhydraulic pump 125 as previously described. Cable feed unit 293 is alsosupported by frame 292.

Cable feed unit 293 includes first drive motor 294 and first idler 295about which extends first drive belt 297. Further included is seconddrive motor 298, second idler 299 and second belt 300. Motors 294 and298 are driven by pump 125 through high pressure supply line 302 andreturn line 303. Belts 297 and 300 frictionally receive cable 54therebetween and are rotated by the respective motors to draw cable 54from reel 55 in a direction indicated by the arrowed line S. Guide tube304 conveys cable 54 from cable feed unit 293 to the inlet end ofsubduct 33.

The foregoing described units cooperate as an integrated apparatus forinstalling a signal transmission cable in a previously preparedsubterranean facility. The function of the several units and theinteraction therebetween will now be described in detail.

The several units, primary unit 50, relay unit 52 and pusher unit 53,along with supply reel 55 and take-up reel 58 are transported to thesite of the subterranean facility by any convenient means, especiallyone or more motorized vehicles such as trucks. For ease oftransportation and to prevent damage, it is recommended that theportions of units 50 and 52 are disassembled and transported separately.Especially noted is that portion, including infeed cable guide 85 andoutfeed cable guide 87, depending below frame 63. The several powerunits may also be transported separately.

Utility unit 170 is secured, preferably near an edge, of the bed of aselected vehicle. Hoist unit 190 is used to lift each of the units fromthe transport vehicle and position as graphically represented in FIG. 1.Supply reel 55 may be similarly positioned or, alternately, left aboardthe transport vehicle. The vehicle carrying the utility unit 170 is thenpositioned downstream of the exit vault to locate the take-up reel 58.

It is within the scope of the instant invention that a hoist unit 190 beincorporated into the power unit 62 of the primary unit 50 and eachrelay unit 52. The pusher unit 53 may also include a hoist unit 190.Accordingly, each unit is self contained and may be transported upon aseparate vehicle.

After each unit is positioned, the depending portion thereof and thepower unit, as best illustrated in FIGS. 2, 4 and 5, is assembled. Afitting 155 is coupled with the inlet end of each segment of thesubduct. After having the upstream end of the cable passed therethrough,guide tube 304 is positioned with the outlet end in communication withthe respective fitting 155 and the inlet end communicating with pusherunit 53. At each access vault, the downstream terminal portion of pullline 57 extending from the upstream segment of the subduct is spliced tothe upstream terminal portion extending from the upstream end of therespective downstream segment of the subduct. Similarly, the upstreamend of pull line 57 is connected to the lead end of cable 54 from supplyreel 55. Accordingly, the several sections of the pull line 57 and thesignal transmission cable 54 are joined to form an elongate flexiblemember.

A substantial length of slack pull line 57 resides within each accessvault 23 and within the exit vault 22. Working in a direction from thedownstream end of the upstream subduct segment, i.e., end 39 of segment37 as seen in FIG. 1, pull line 57 is passed over infeed guide 85 andwound in several coils about capstan wheel 80. The line is wound with aninitial coil at the rearward or inboard edge of surface 84 with eachsuccessive coil being placed forwardly as best seen with reference toFIG. 3. After the coils are in place, the line is passed upwardly overintermediate cable guide 112 and then downwardly around outfeed cableguide 87. At the exit vault 28, the line is similarly passed over therespective infeed cable guide 85 and wound about the capstan wheel 80 ofthe primary unit 50. Finally, the downstream terminal portion of theline 57 is fixed to take-up reel 58. The apparatus is now readied forpulling the elongate flexible member, initially pull line 57 andsubsequently signal transmission cable 54, through the subduct 33.

Initially, each shuttle valve 137 is adjusted to a selected setting toprovide relief at a maximum pulling force as predetermined by thetensile strength of the signal transmission cable. Each intermediatecable guide 112 is oriented, by means of adjusting screw 119 alteringthe effective length of spring 117, to reside in the fully up positionand compensate for weight, bending resistance and other factorsassociated with the flexible member as will be appreciated by thoseskilled in the art. Finally, with each control lever 129 moved to aninitial position to curtail any output from the associated pump, therespective internal combustion engine 122 is started. The apparatus isnow readied for pulling the elongate flexible member, initially pullline 57 and subsequently signal transmission cable 54, through thesubduct 33. Slack in the downstream terminal portion of pull line 57 isnow wound about take-up reel 58. This action also tightens the pull lineabout the capstan wheel 80 of primary unit 52 for frictional drivingengagement. It is noted that the pull exerted by reel 58 is sufficientonly for the purpose of taking up slack and is substantially below thatrequired to rotate the capstan wheel of the primary unit to pull linefrom the subduct 33.

With relay unit 52 and pusher unit 53 standing at idle, rotation ofcapstan wheel 80 associated with primary unit 50 is initiated bymovement of the respective control lever 129. Simultaneously, rotationof take up reel 58 is initiated. A sequence of events then follows.First, slack pull line 57 intermediate primary unit 50 and take up reel58 is wound about take up reel 58. In response to continued rotation oftake up reel 58, the coils of pull line 57 encircling capstan wheel 80of primary unit 50 are tightened and brought into frictional drivingengagement. Accordingly, primary unit 50 exerts a pulling tension uponpull line 57 to commence movement thereof. It is noted that the pullexerted by reel 58 is sufficient only for the purpose of taking up slackand is substantially below that required to rotate the capstan wheel ofthe primary unit to pull cable from the subduct.

Initially, primary unit 50 functions to pull slack cable within exitvault 28, more specifically intermediate capstan wheel 80 and thedownstream end 35 of subduct segment 38. Next, cable 57 commencesmovement through subduct segment 38 taking up slack within access vault23 intermediate the upstream end 40 of subduct segment 38 and thecapstan wheel 80 of relay unit 52. As pull line 57 continues to move, itis brought into firm engagement with out feed cable guide 87 atintermediate cable guide 112. Subsequently the coils of pull line 57 aretightened into friction engagement with capstan wheel 80 of relay unit52. In response to continued movement, as a result of the pullingtension exerted by primary unit 50, pull line 57 pulls intermediatecable guide 112 of relay unit 52 downwardly to move lever 27 and supplypressurized hydraulic fluid to motor 73 for rotation of capstans wheel80. Should the installation and apparatus include additional upstreamrelay units 52, each will be operated in sequence in response to theadjacent downstream unit analogous to the above described response ofrelay unit 52 to primary unit 50. After all slack has been removed fromthe cable within entrance vault 20, pusher unit 53 is initiated to pullsignal transmission cable 54 from supply reel 55.

It is apparent from the foregoing description that each relay unit 52 isresponsive to the adjacent downstream pulling unit, either primary unit50 or another relay unit 52. Communication between adjacent units isthrough the elongate flexible member. Each subsequent unit responds topull and relay the elongate flexible member at a speed which ispredetermined by the speed at which the member is pulled by the adjacentdownstream unit. Referring more specifically to FIG. 12, there is seen,in diagrammatic representation, primary unit 50 and relay unit 52 havingrespective capstan wheels 80. Relay unit 52 further includesintermediate cable guide 112. Also illustrated is subduct 33 havinginlet end 34 and outlet end 35. Pull line 57, the initial portion of theelongate flexible member, extends through subduct 33 and is engaged witheach capstan wheel 80. After engagement with capstan wheel 80 of relayunit 52, pull line 57 extends over intermediate cable guide 112 enrouteto be relayed to primary unit 50.

With regard to primary unit 50, motor 73 rotates capstan wheel 80 in adirection with predetermined velocity and force represented by thearcuate arrowed line designated R₁. Accordingly, a predetermined tensionrepresented by the arrowed line T₁ is exerted upon pull line 57 to pullline 57 through subduct 33 at a speed, direction and rate of movement,as represented by the arrowed line designated S₁.

Motor 73 of relay unit 52 is capable of rotating the associated capstanwheel 80 in a direction with a speed and a force as represented by thearcuate arrowed line R₂. In response thereto pull line 57 is pulled fromthe preceding subduct segment and is supplied to intermediate cableguide 112 at a relay speed represented by the arrowed line S₂. It willbe appreciated that pull line 57 leaving intermediate cable guide 112moves at the previously described speed S₁. Tension on pull line 57leaving intermediate cable guide 112 is represented by the arrowed lineT₂. Tension T₂ is equal to the tension T₁ minus losses due to frictionand other factors as pull line 57 moves through subduct 33. Intermediatecable guide 112 is held in equilibrium between the forces represented bythe arrowed lines F₁ and F₂. Force F₁ is the result of the upwardbiasing of spring 117. Initially, force F₂ is the combined weight of arm109, intermediate cable guide 112 and the static weight of a portion ofpull line 57.

For purposes of explanation, it can be considered that the primary unit50 and the relay unit 52 cooperate through four phases of operation asdiagrammatically represented in FIG. 13. The phases are rest,acceleration, normal pull and deceleration. The phases are related tothe positioning of intermediate cable guide 112 as represented by theline X. For further orientation, line X is plotted against the movementof intermediate cable guide 112 represented by the double arrowed linedesignated Y and time extending in the direction indicated by thearrowed line Z.

During the phases of rest and normal pull, the apparatus is in theequilibrium. During the phases of acceleration and deceleration, theapparatus is not in equilibrium. It is the function of intermediatecable guide 112, to sense imbalance and bring the apparatus intoequilibrium as will be now described.

During the initial rest phase, neither capstan wheel 80 is rotating.Accordingly, R₁, R₂, T₁, T₂, S₁ and S₂ have a value of zero.

The acceleration phase is initiated by supplying pressurized hydraulicfluid to motor 73 for rotation of capstan wheel 80 associated withprimary unit 50. Accordingly, the values of R₁, T₁ and S₁ increase to apredetermined value. Initially, capstan wheel 80 associated with relayunit 52 remains at rest. Correspondingly, the value of S₂ is zero.Stated in other words, the value of S₁ exceeds the value of S₂. Inresponse to continued movement of line 57 as represented by the arrowedline S₁, intermediate cable guide 112 is drawn downwardly against thebiasing force F₁. Correspondingly, pressurized hydraulic fluid issupplied to motor 73 for rotation of capstan wheel 80 of relay unit 52.The downward movement of intermediate cable guide 112 continues untilthe value of S₂ equals the value of S₁. It is apparent that at thispoint the value of R₂ equals the value of R₁. With all forces equalized,the apparatus is in equilibrium and precedes through the phase of normalpull.

When it is desired to cease operation, the supply of hydraulic fluid tomotor 73 of primary unit 50 is curtailed to bring the associated capstanwheel 80 to a stop. Initially, the speed of pull line 57 represented bythe arrowed line S₁ exceeds the speed represented by the arrowed lineS₂. Accordingly, intermediate cable guide 112 moves upwardly therebydecreasing the value of R₂ in proportion to the decrease in the value ofR₁. The deceleration phase continues until the apparatus achieves thefinal rest phase in which the apparatus is again in equilibrium.

As will be appreciated by those skilled in the art, fluctuations infriction and other forces resisting the movement of pull line 57 throughsubduct 33 will result in fluctuations of the value of the movementspeed of line 57 as represented by the arrowed line S₁. Intermediatecable guide 112, responsive to the differential between the values of S₁and S₂, will move accordingly to alter the speed of capstans wheel 80associated with relay unit 52 as represented by the arcuate arrowed lineR₂. It is apparent, therefore, that relay unit 52 is responsive toprimary unit 50 through the communication provided by pull line 57. Itis equally apparent that the response of relay unit 52 is dictated bythe speed at which primary unit 50 pulls pull line 57. It is also notedthat lubrication unit 123, being in series with motor 73, supplieslubricant to pull line 57 at a rate which is proportional to the speedof pull line 57 as represented by the arrowed line S₁.

Each unit, primary and relay, is also responsive to the stress on theincoming or immediate upstream segment of the flexible member. Arelative force is exerted upon the infeed cable guide 85, which isreceived by the piston and cylinder assembly 99 and relayed to reliefvalve 137 which functions to controllably govern the operation ofcapstan wheel 80. The valve 137 curtails the flow of pressurizedhydraulic fluid to motor 73 as necessary to maintain pulling stress ortension within the selected limit.

Turning now to FIG. 14 a system for stringing an airborne signaltransmission cable 310 is illustrated. Air borne cable 310 is pulledfrom a supply spool 312 and supported by a support cable 313 generallyspanning a plurality of poles 314, in accordance with conventionalpractice. Typically, a pull line 315 has an end 316 coupled to an end317 of cable 310 as can be seen with additional reference to FIG. 15.Pull line 315 is then coupled to a pull vehicle 318. In the immediateembodiment, pull vehicle 318 is a boom truck having a basket 319 at theend of a boom 320 which may be raised to the level of support cable 313.As cable 310 is pulled from supply spool 312, an operator ensconced inbasket 319 periodically attaches removable pulleys 322 which supportsignal transmission cable 310 from support cable 313. Pull line 315 andsubsequently cable 310 are pulled along pulleys 322 in a directionindicated by arrowed line AA. Cable 310 may be pulled in this manneruntil either, cable 310 runs out, the distance to cover is spanned orthe tension on the cable reaches a point where damage would occur withfurther pulling. It is at this point that a drive out controller systemgenerally designated 325 is indispensable.

Referring specifically to FIG. 15, drive out controller system 325includes a tension relief mechanism 327 coupled to pull vehicle 318, atensometer 328 for sensing the tension forces sustained by cable 310 andcontrol system 329 (with additional reference to FIG. 16) for receivingsignals from tensometer 328 and controlling tension relief mechanism327. Tension relief mechanism 327 may be coupled to the back of a pullvehicle, or coupled to basket 319 of the boom truck. Tension reliefmechanism 327 includes a rotatable spool 330 supported by a clevis 332.Clevis 332 is securely mounted to pull vehicle 318 and rotatably carriesspool 330, the rotation thereof subject to the influences of a stopmechanism 333 and a brake 334, also carried thereby. Brake 334, carriedby clevis 332 adjacent spool 330, imparts a drag on the rotation ofspool 330, the purpose of which will be addressed in the ensuingdescription of the operation of drive out controller system 325. Stopmechanism 333 may be any conventionally known apparatus for preventingrotation of spool 330 with respect to clevis 332, such as a ratchet andpawl, a brake having two positions, to completely stop spool 330 and toact as a drag (FIG. 17) or, as illustrated in FIG. 15, a pin 335actuated by a motor 337, mounted on clevis 332. Pin 335 is movable bymotor 337 between an extended position in which it engages and preventsrotation of spool 330, and a retracted position in which it allowsrotation of spool 330 upon receipt of a signal from control system 329.

Still referring to FIG. 15, pull line 315 coupled to end 317 of cable310, extends over pulleys 322 along support cable 313, passes throughtensometer 328, and is coupled to spool 330. For proper operation ofdrive out controller system 325, an excess of pull line 315 is carriedby spool 330 in anticipation of use during the pulling process. In thisembodiment, tensometer 328 is fixed to vehicle 318 proximate tensionrelief mechanism 327 with pull line 315 extending therethrough totension relief mechanism 327. Various configurations have beencontemplated, including coupling tension relief mechanism 327 to vehicle318 and tensometer 328 to basket 319, or both to vehicle 318. Tensometer328 is illustrated as being what is commonly referred to as a runningline tensometer. This refers to its characteristic of allowing the lineto run freely through three rotating wheels 338 while sensing tension oncable 310. It is this characteristic which permits it to be fixed tovehicle 318. The importance of this aspect will be discussedsubsequently.

Those skilled in the art will realize that substantially any tensometeror like device may be employed, for example, tensometer 328 may bereplaced with a tensometer 340 as illustrated with additional referenceto FIG. 16. Tensometer 340 is free from vehicle 318 and couples end 317of cable 340 to end 316 of pull line 315. This type of tensometer isfixed in relation to its position on cable 310, therefore it cannot beattached to vehicle 318 in this embodiment. A control cable 342 with aquick release coupler 343 couples tensometer 340 to control system 329.Control system 329 preferably includes a display and control unit 344which receives and decodes signals from the tensometers. Control system329 may also include a permanent recorder 345 which will print out ahard copy of the tension forces generated. Display and control unit 344provides information to the operator of vehicle 318 in various mannerssuch as by a gauge, digital readout or the like for impartinginformation to the operator in a visually manner, and/or audio signalssuch as bells, whistles, beeps or the like. Display and control unitsare well known in the art, and any may be employed. Control system 329is in communication with, and upon receipt of a predetermined tensionforce sends a signal to stop mechanism 333 of tension relief mechanism327 (FIG. 15).

It will be understood that FIG. 16 is intended to represent thereplacement of tensometer 328 with tensometer 340 within drive outcontroller system 325, other elements remaining substantially unchangedunless specifically addressed. While FIG. 15 alone illustrates tensionrelief mechanism 327, it is intended that pull line 315 and control unit344 of FIG. 16 are also coupled to tension relief mechanism 327 althoughnot specifically illustrated. Furthermore, while FIG. 16 illustratescontrol system 329, it is intended that tension relief mechanism 327 andtensometer 328 are also coupled to control system although notspecifically illustrated. In other words, FIGS. 15 and 16 togetherillustrate substantially the entirety of drive out controller system325, differing only in replacement of the tensometers.

During operation, tension relief mechanism 327 is in a locked statewherein stop mechanism 333 engages spool 330 preventing rotation thereofas vehicle 318 pulls cable 310 from supply spool 312, stringing it alongsupport cable 313. As cable 310 is pulled, tensometer 328 or 340measures the tension on cable 310. Signals from tensometer 328 or 340are communicated with control system 329. This provides the vehicleoperator with information on the tension forces being applied to cable310. Preferably two tension force values are determined prior to pullingand programmed into control system 329. Control system 329 preferablyfurther includes a security system, such as a mechanical combination ondisplay and controller unit 344, or a requirement for a password builtinto the software thereof, to prevent the tension values from beingchanged without appropriate authorization. The first tension value isthe lower, and is comparable to a caution zone. The second tension valueis the value not to be exceeded. Upon receiving a signal from tensometer328 or 340 that the first tension value has been reached, control system329 signals the operator for caution. At this point the operatorrealizes he is coming to the pull limit, or a snag is developing. He mayelect to stop at that point or continue. Upon reaching the second value,control system 329 switches tension relief mechanism to an unlockedstate by sending a signal to motor 337 of stop mechanism 333 causing pin335 to be retracted, and allowing spool 330 to rotate under the pullforce. Rotation of spool 330 allows the tension to diminish as pull line315 is spooled off of spool 330. Brake 334 produces a drag on spool 330to prevent free rotation thereof which would result in cable 310stripping pull line 315 off spool 330 by its weight, and sagging betweenpoles 314. This is undesirable for numerous reasons including producinga hazard such as by sagging over a roadway.

The release of spool 330 prevents a suddenly developed snag fromdamaging cable 310. Before the operator can react, control system 329will switch tension relief mechanism 327 to the unlocked state releasingspool 330 and reducing tension. The operator may then stop and correctthe problem. In another scenario, the operator has reached the criticaltension, but cannot stop for some reason. He may proceed for a distance,until the pull line carried by spool 330 is gone. This should give himplenty of time or distance.

Referring back specifically to FIG. 15, it can now be fully appreciatedthat the free movement of pull line 315 through tensometer 328 allowstensometer 328 to be fixed to vehicle 318. Upon release of spool 330,pull line 315 will move through tensometer 328. The same occurrence whentensometer 340 is used (FIG. 16), requires that quick release coupler343 couple control cable 342 to tensometer 340. Upon release of spool330, tensometer 340 will move away from vehicle 318 with cable 310 aspull line 315 unspools. If control cable 342 cannot break away fromtensometer 340, either or both may be damaged.

Turning now to FIG. 17, a further embodiment of a drive out controllersystem generally designated 350 is illustrated. In this embodiment, atension release mechanism 352 including a spool 353 rotatably carriedwithin a clevis 354, is coupled to a pull vehicle 355 by a tensometer357 generally similar to tensometer 340. Spool 353 is prevented fromrotating by a stop mechanism which, in this embodiment, is included in abrake 358. In this embodiment, brake 358 has two function. It preventsrotation of spool 353 until a signal is received from control system(not shown) as described previously in connection with FIGS. 15 and 16,then it opens, releasing spool 353 and providing a drag on the rotationof spool 353. While brake 358 is used in this embodiment to act both asa stop and a drag, it will be understood that the previously describedelements may also be used.

While the drive out control system prevents exceeding a predeterminedtension on a cable, it does not allow a longer cable run. Asubstantially longer cable run can be achieved by employing relay unit52 as described previously. Relay unit 52 may be positioned on theground and include a brace 360 engaging a pole 362 to provide additionalstability. However it is not intended that the positioning of relay unit52 be limited to this approach. A cable 363 would be pulled to itslimit, then extended from a pulley 364 to capstan wheel 80. Cable 363would engage relay unit 52 in substantially the same manner as describedpreviously in connection with subterranean pulling, except that cable363 would extend downward from pulley 364 instead of upward from accessvault 23. Cable 363 can then be pulled by a vehicle for another run,assisted by relay unit 52 in the same manner as described previously.Additional relay units may be used as the run progresses.

To provide a motive force proportional to the rotation of capstan wheel80 of relay unit 52 or primary unit 50, a driving device generallydesignated 370 is employed as illustrated in FIGS. 19 and 20. Drivingdevice 370 includes a drive gear 372 engaging the inner surface ofcapstan wheel 80. As capstan wheel 80 rotates, drive gear 372 is rotatedproportionally. An end 374 of a flexible drive shaft 373 is coupled todrive gear 372 and as capstan wheel 80 rotates in a direction indicatedby arcuate arrowed line BB, drive gear 372 and flexible drive shaft 373are rotated in a direction indicated by arcuate arrowed line CC. Anopposing end 375 of drive shaft 373 may be coupled to various drivendevices to accomplish different tasks.

Referring specifically to FIG. 19 primary unit 50 is illustrated.Opposing end 375 of drive shaft 373 is coupled to a driven wheel 377,which rotates at the same rate as drive gear 372. A clamp wheel 378 ispositioned adjacent driven wheel 377 with a space therebetween forreceiving a pull line 379. Driven wheel 377 and clamp wheel 378 receivepull line 379 from capstan wheel 80 therebetween, and spool it neatlyinto a container 380 at a rate identical to the rotation of capstanwheel 80. Using the rotation of capstan wheel 80 to drive driving device370 ensures that collection of pull line 379 progresses at a ratecompatible with capstan wheel 80. Furthermore, the collection of pullline 379 between driven wheel 377 and clamping wheel 378 provides thenecessary friction coupling of pull line 379 on capstan wheel 80 for itsproper operation.

Referring specifically to FIG. 20, capstan wheel 80 of either relay unit52 or primary unit 50 is illustrated. Opposing end 375 of drive shaft373 is coupled to a rotary pump 382. Rotation of drive shaft 373 crankspump 382 which can be used to pump lubricant from a container 383 via ahose 384, to fitting 155 of subduct 33 via lubrication line 154,previously illustrated in FIG. 2. Pump 382, operated by driving device370, replaces the complicated lubricating unit 122 illustrated in FIG.2. Furthermore, the lubricant will be pumped at a rate proportional tothe rotation of capstan wheel 80.

Various changes and modifications to the embodiment herein chosen forpurposes of illustration will readily occur to those skilled in the art.To the extent that such modifications and variations do not depart fromthe spirit of the invention, they are intended to be included within thescope thereof which is assessed only by a fair interpretation of thefollowing claims.

Having fully described the invention in such clear and concise terms asto enable those skilled in the art to understand and practice the same,the invention claimed is:
 1. A method for pulling cable through a space,said space including:an upstream end, a downstream end, and a pointintermediate said ends dividing said space into a first segment adjacentsaid upstream end and a second segment adjacent said downstream end,said method comprising:pulling said cable from the downstream end ofsaid space, including exerting a tension on said cable in a direction;sensing movement of said cable proximate said intermediate point;applying a downstream pull on said cable proximate said point inresponse to said movement; directly and continuously monitoring thetension on said cable being pulled at the downstream end; discontinuingpulling said cable at the downstream end in response to said tensionexceeding a predetermined value; directly and continuously monitoringthe tension on said cable being pulled proximate the point; anddiscontinuing pulling said cable proximate the point in response to saidtension exceeding a predetermined value.
 2. The method of claim 1,wherein said monitoring tension on said cable includes:applying a forceto a moveable element in response to the tension on said cable; andopposing movement of said element with a counterforce of saidpredetermined value.
 3. The method of claim 1, furtherincluding:selectively varying said predetermined value.
 4. The method ofclaim 3, further including:selectively varying the predetermined valueof said counterforce.
 5. The method of claim 1, wherein said applying adownstream pull on said cable includes:drawing said cable from the firstsegment; and relaying said cable pulled from the first segment to thesecond segment.
 6. The method of claim 5, further including:sensingmovement of said cable proximate said point resulting from said pulling;and commencing said drawing and said relaying in response to sensingmovement of said cable proximate said point.
 7. The method of claim 5,further including:sensing rate of movement of said cable proximate saidpoint resulting from said pulling; and regulating said drawing and saidrelaying to proceed at a rate of speed to achieve equilibrium with saidrate of movement.
 8. The method of claim 7, wherein said regulatingincludes:accelerating said drawing and said relaying when said rate ofmovement is greater than said rate of speed; and decelerating saiddrawing and said relaying when said rate of movement is lesser than saidrate of speed.
 9. The method of claim 1, further including:lubricatingsaid cable at a quantitative rate proportional to a rate at which saidcable is pulled through said space.
 10. A method for pulling a cablethrough a space, said space including:an upstream end, a downstream end,and a point intermediate said ends dividing said space into a firstsegment adjacent said upstream end and a second segment adjacent saiddownstream end, said method comprising:placing first pulling meansproximate said downstream end; placing second pulling means proximatesaid point; engaging a portion of said cable with said first pullingmeans; engaging an intermediate portion of said cable with said secondpulling means; driving said first pulling means and said second pullingmeans for pulling said cable through said second and said firstsegments, respectively, of said space; guiding said cable from thedownstream end of said space to said first pulling means,including:bearing said cable against first guide means for receivingsaid cable from said downstream end of said space and directing saidcable to said first pulling means; directly and continuously monitoringa first force applied to said first guide means by said cable;discontinuing driving said first pulling means in response to said firstforce exceeding a predetermined value; guiding said cable from the firstsegment of said space to said second pulling means, including:bearingsaid cable against second guide means for receiving said cable from saidspace proximate said point and directing said cable to said secondpulling means; directly and continuously monitoring a second forceapplied to said second guide means by said cable; and discontinuingdriving said second pulling means in response to said second forceexceeding a predetermined value; and subsequently guiding said cablefrom said second pulling means to the second segment of said space. 11.The method of claim 10, wherein said guiding includes:receiving saidcable along a first axis which is substantially coaxial with adownstream terminal portion of said space; and directing said cable tosaid first pulling means along a second axis which is angularly disposedto said first axis.
 12. The method of claim 10, wherein:said guidingincludes: receiving said cable along a first axis which is substantiallycoaxial with a downstream terminal portion of the first segment of saidspace; and redirecting said cable to said second pulling means along asecond axis which is angularly disposed to said first axis; and saidsubsequently guiding includes receiving said cable from said pullingmeans along a third axis, and redirecting said cable to the secondsegment of said space along an axis which is substantially coaxial withan upstream terminal portion of said second segment.
 13. The method ofclaim 10, wherein said driving further includes:controlling said secondpulling means in response to pulling of said cable by said first pullingmeans.
 14. The method of claim 10, further including:bearing said cableagainst a moveable element prior to guiding said member to the secondsegment of said space; determining force resulting from a differentialbetween a first rate of speed at which said cable is pulled from saidsecond segment and a second rate of speed at which said cable is pullingfrom said first segment by movement of said moveable element; andcontrolling driving said second pulling means in response to movement ofsaid moveable element.
 15. The method of claim 10, furtherincluding:applying a lubricant to said cable upstream of each segment ofsaid space at a quantitative rate proportional to the rate at which saidcable moves through said space.